1. Field of the Invention
The present invention relates generally to reciprocating internal combustion engines, and more specifically to a novel combustion chamber configuration for such engines which results in unexpected and substantial improvements in power, economy, and exhaust emissions. The combustion chamber configuration is particularly adaptable to four stroke, spark ignition or Otto cycle automobile engines having multiple cylinders, but may be adapted to other single and multiple cylinder reciprocating engines as well, such as Diesel engines, etc.
2. Description of the Related Art
Since the initial development of the reciprocating internal combustion engine in the latter part of the nineteenth century, numerous variations and improvements have been developed. Over the years, the four stroke, spark ignition (or "Otto cycle") engine with overhead intake and exhaust valves has been nearly universally accepted for use in most motor vehicles, including automobiles, boats, and aircraft. Other reciprocating engine types (two stroke cycle, two and four stroke compression ignition or Diesel cycle, etc.) have also been developed for such use, but are in the minority.
It is generally accepted that the well proven Otto cycle engine enjoys various advantages over other engine types, such as relatively low weight for the power output, relatively good fuel economy, general availability of fuel, economy of construction, and low maintenance. However, most reciprocating internal combustion engines have been burdened with an additional requirement in the latter part of the twentieth century: The requirement to produce relatively low exhaust emissions from their power output.
Experiments have been performed with all of the various types of engines mentioned above, and others, in attempting to reduce exhaust emissions to minimal levels while still maintaining the "drivability" of the engine (i. e., ease of starting when warm or cold, throttle response, power, fuel economy, etc.). Generally, it has been found that the easiest way of "cleaning up" the exhaust of most engines is to install one or more catalytic converters in the exhaust system, to complete the oxidation process of any unburned hydrocarbons which may exit the combustion chamber(s) of the engine. Other than this, various means have been used to reduce oxides of nitrogen emissions, which generally occur in relatively high temperature combustion due to high compression ratios. Accordingly, compression ratios have been reduced in the past in an attempt to reduce oxides of nitrogen emissions, but this has generally been at the expense of unburned hydrocarbons, which are then handled by catalytic converters in the exhaust system. Otherwise, there have been few, if any, modifications to the classic combustion chamber configuration of the Otto cycle engine.
Accordingly, a need will be seen for an internal engine modification which reduces various types of exhaust emissions, such as unburned hydrocarbons and oxides of nitrogen, while reducing dependence upon exhaust system modifications or additions, such as catalytic converter systems. The modification comprises a new combustion chamber configuration which is particularly adapted to Otto cycle internal combustion engines, but which may be adapted to two stroke cycle engines, compression ignition or Diesel engines of two and four stroke cycles, and other reciprocating engine configurations as well. The combustion chamber modification must also produce reasonable power and fuel economy, or at least not reduce those qualities, while at the same time reducing exhaust emissions.
While the present combustion chamber configuration does not completely eliminate undesirable exhaust emissions, it does, in combination with catalytic converter exhaust systems, reduce such emissions to well below the maximum allowable levels of emissions for current new vehicles, thus allowing the catalytic converter exhaust systems used with such engines to be reduced in size, weight, and expense for greater efficiency, or for the engine to meet exhaust standards anticipated for ultra low emissions vehicles while using a conventional catalytic converter exhaust system. A discussion of the related art known to the inventors, and the differences and distinctions between those devices of the related art and the present invention, is provided immediately below.
U.S. Pat. No. 2,347,097 issued on Apr. 18, 1944 to Earl Ginn et al. describes a Cylinder Head And Combustion Chamber Construction incorporating various features, among them a combustion chamber having an elongate or ovoid volumetric pocket for the two intake and exhaust valves and the spark plug. The concept is to provide sufficient room for the actuation of the conventional poppet valves downwardly into the combustion chamber, while removing the proximity of those valves from the sides of the combustion chamber and upper cylinder walls. While Ginn et al. note that the resulting chamber shape is "somewhat spherical in contour" (column 2, line 37), this is not precisely correct, as the shape is actually somewhat ovoid, as may be seen in the cross sections of FIGS. 3, 4, and 5 of the Ginn et al. patent. This results in a relatively flattened ledge to each side of the ovoid combustion chamber which overlies a part of the underlying cylinder, as shown in FIG. 5 of the Ginn et al. patent. Such ledges within the combustion chamber are now known to be disadvantageous, as they (1) increase the "quench" area of the combustion chamber by increasing the surface area of the chamber relative to the volume of the chamber, and (2) provide additional relatively abrupt and sharp edges in the chamber, which lead to localized hot spots and potential preignition and detonation, and which also disrupt smooth gas flow in the combustion chamber. The present combustion chamber configuration eliminates the flattened ledge of earlier combustion chambers, and smoothes the internal surfaces of the chamber to smooth gas flow and eliminate sharp edges.
U.S. Pat. No. 2,878,800 issued on Mar. 24, 1959 to Gilbert Burrell describes a Frusto Conical Combustion Chamber And Method Of Making Same. The object of the Burrell disclosure is to reduce substantially the excess volume of the combustion chamber, which extends beyond the upper edges of the cylinder. This provides a relatively sharp edge along the upper edge of the cylinder which leads to preignition and detonation, as noted above in the discussion of the Ginn et al. disclosure. Burrell recognizes this problem, as evidenced in column 1, lines 39-40 of his patent. However, the Burrell combustion chamber does not completely eliminate this overhanging "pocket" of the combustion chamber extending beyond the periphery of the cylinder, as shown clearly in FIG. 2 of the Burrell patent. Moreover, the Burrell combustion chamber is a wedge shaped chamber, which while being reasonably efficient, also produces a relatively large quench area opposite the spark plug, with its resulting reduction in combustion temperature due to the relatively large amount of surface area per volume and the resulting increases in unburned hydrocarbons. The present combustion chamber essentially eliminates such quench areas, while also smoothing any edges and the like within the chamber and chamber/cylinder interface, to eliminate or at least greatly reduce the potential preignition, detonation, and unburned hydrocarbon emissions problems which can be caused by such configurations.
U.S. Pat. No. 2,954,023 issued on Sep. 27, 1960 to Aurelio Lampredi describes a Combustion Chamber For Internal Combustion Engines, comprising a shape formed of a plurality of non-concentric hemispherical sections. The result is not a true hemispherical chamber, and is far removed from the present chamber, with its combination of hemispherical and wedge shapes and substantial reduction of quench areas and preignition producing sharp edges.
U.S. Pat. No. 2,991,780 issued on Jul. 11, 1961 to Wayne V. Brien describes Combustion Chambers For Internal Combustion Engines formed of a plurality of intersecting geometric shapes for ease of manufacture. Brien states that quench areas are important to cool the last of the burning mixture to avoid detonation, but the last portion of the combustion does not occur until the piston is moving away from the cylinder head and combustion chamber, thereby eliminating any close spacing or quench area between piston and cylinder head. The primary purpose for such close spacing at top dead center of the piston, is to provide the desired high compression ratio for high efficiency of the engine. In any event, the present combustion chamber teaches away from the relatively sharp edges produced by the multiple geometric shapes defining the Brien combustion chamber, by providing a smoothly contoured combustion chamber having a relatively high compression ratio due to the semi-wedge configuration, but also greatly reducing or eliminating substantial quench areas and edges which might lead to preignition and detonation.
U.S. Pat. No. 5,257,612 issued on Nov. 2, 1993 to Richard W. Smith, Jr. et al. describes an In-Line Cylinder Head For An Internal Combustion Engine. The combustion chamber described is basically that of a General Motors small block V-8 from 302 to 350 cubic inches. The intake passages of the head are modified, but the combustion chamber configuration appears to be no more than slightly modified from the stock configuration of the GM small block V-8. While the present disclosure is also based upon the GM small block V-8 head, the combustion chamber shape is modified substantially from that of the stock configuration, and from the configuration shown in Smith, Jr. et al. Smith, Jr. et al. provide a ridge extending between intake and exhaust valves, which ridge is smoothed and reduced substantially in the present combustion chamber. Smith, Jr. et al. state that the ridge assists in reducing crossover from intake flow to the exhaust port when valve overlap occurs at the top of the exhaust stroke, but such crossover is minimal on most engines due to both intake and exhaust valves being nearly closed when the piston is at top dead center of its travel in order to preclude interference between the piston crown and the valves. Smith Jr. et al. also do nothing to eliminate the large flat surface of the combustion chamber opposite the spark plug, which produces a large quench area at top dead center of the piston stroke. The present chamber opens this area up considerably to reduce combustion heat loss from the otherwise relatively large surface area per volume ratio, thus increasing thermal efficiency and reducing unburned hydrocarbons due to incomplete combustion.
British Patent Publication No. 722,149 published on Jan. 19, 1955 to Ronald F. Golding et al. describes Improvements In Or Relating To Combustion Chambers Of Internal Combustion Engines. Golding et al. provide a "lozenge shape" (page 1, line 62) or oval combustion chamber, having extensive quench areas to opposite sides of the intake and exhaust valves. The undesirability of such quench areas has been noted further above. Golding et al. further provide a ledge or discontinuity in the side of the combustion chamber, to deflect the incoming intake charge from the exhaust valve in order to reduce the possibility of preignition of the charge due to contact with the hot exhaust valve. This teaches away from one of the points of the Smith, Jr. et al. patent discussed immediately above, in that Smith, Jr. et al. provided for circulation of the incoming fuel and air charge over the exhaust valve for cooling of the valve. Thus, two different theories of operation are disclosed in these two patent documents, neither of which describe or suggest the specific improvements provided by the present combustion chamber configuration for reducing emissions and increasing efficiency.
Japanese Patent Publication No. 52-54820 published on May 4, 1977 illustrates a combustion chamber configuration having a predetermined hemispherical radius centered on the spark plug electrode. Cross sections of other combustion chamber shapes are also shown, but none appear to have the characteristics or configuration of the combustion chamber of the present invention.
Finally, Japanese Patent Publication No. 52-64511 published on May 28, 1977 illustrates an internal combustion engine having a combustion chamber configuration essentially identical to that of the 54820 Japanese patent publication discussed immediately above. According to the English abstract, the 64511 patent publication also includes a three way catalytic converter, exhaust gas analyzing means, and fuel control means in combination with the specific combustion chamber configurations. In any event, as the combustion chamber configurations appear to be essentially identical with those of the 54820 patent publication, no similarity is seen to the present combustion chamber configuration.
None of the above inventions and patents, either singly or in combination, is seen to describe the instant invention as claimed.